Manufacture of electrotype printing plates



Nov. 5, `1940. I H. M. BLAETZ 2,220,671

MANUFACTURE OF LECTRQTYPE PRINTING PLATES Filed Oct. 16, 1937 CLWM, moigm Mw. ArraA/EK Patented'Nov. 5, 1940 MANUFAC'IURJ] 0F ELECTROTYPE PRINT- V ING PLATES Y Harry M. Blaetz, Haddoneld, N. J., assignor to The Cnrtisvlublishng Company, Philadelphia, Pa., a corporation of Pennsylvania "1 Application October 16, 1937, Serial No. 169,389

. 2 Claims.

'I'lie object -oirl the present invention is Vto lo condition the plates during the process of manufacture thatrelative level differentials may be'impressedinto the face yof the plate in k5 all areas, either large orsmall, that may require ksuch diilerentials for-the proper reproduction of the various tone values during the printing operation. v

Other objects of the invention will appear from the following vdescription at the end of whichthe invention will bevclaimed.

Generally stated the invention consists in heating a partially completed electrotype plate to a critical temperature-and then quenching or suddenlyI cooling it, A ereby developing in the backing-up lead alloy extreme softness followed after a time intervalby increased hardness and toughness` in respect-to its initial condition, and thereafter and during said ti e interval and while the plate is in softened c' ndition impart- ,l ing level-diierentialslnot only at relatively large' but valso andimaddition at relatively small areas of the plate surface by the application of pressure and a matormatrixcorresponding to both small andV large surface areas of the plate.

The invention also consists in the improvements hereinafter described and finally claimed.

Heretofore it has been customary to\backup a' flat electrotype shell (nickel lfaced copper, both electro-deposited) with lead alloy bonded by tin foil, and to carry the flat plate through most of the operations :involved in completing the plate. When it isnecessaryto McKee treat a plate this operation-is also performed on'the dat plate. This McKeeV treatment consists of hot-pressing the level differentials which constitute the various tone gradationsfinto theface of the plate, `using a vbuilt-up matrix on the face and a female,y lmatrlxon theback, as, for-example, according to McKeePatents U. S. Numbers 988,583 and 1,077,621. This iresults in solid printing areas being raisedand high-light areas being relatively depressed-with areas of intermediate tone values forced lto correspondingly intermediate 45 levels. The'leveldliferentlals between the solid areas-and high-light areas usually amount toy some two to five one-thousandths of an inch. .Theat plate 'is l.curved,-for mounting on the printing'pres's plate cylinder, as one of the finaloperationsinthe Vplate making sequence. The plate maybe curved either hot or cold. u

Standard equipment now available inthe market permits casting orv backing-up a curved shell andcarrying the curved'platel through the entire sequence of operations. Each machine used (Ul. lill-401.3)

has the same press-plate cylinder arc so that the completed plate will i'lt the cylinder perfectly. The equipment also provides forthe McKee treating step when needed. This treatment may be applied by means of a laminated or built-up 5 face matrix in a curved-bed machine equipped with toothed rollers and is completed in a curvedbed shaving machine.

still it works against the' application of proper 20 McKee treatment to the plate. By the time the l' McKee ltreating step has been reached the plate alloy isy so hard that it is feasible to apply leveldifferentials only to comparativelylarge areas of plate surface. `The treatment of small areas, `2E; a quarter of an inch to half aninch in diameter, often necessary for satisfactory printed results must be and is neglected. In an attempt to correct this disadvantage another step has sometimes heretofore been introduced into the operation sequence and it consists in the use of a machine that softens the plate by heating it to about 425 F. which is not a critical temperature. This, however, is only a make-shift.

Heat treating to a critical temperature and then quenching or suddenly cooling the partially completed plate before rolling and shaving' and McKee treating produces an/extreme softness of the plate which persists for some two or three hours and is then followed by a rapid toughen- 40 ing and hardening. The heat treating consists in heating the plate at a temperature of 470 F. more or less for about fifteen minutes followed by rapidcooling asby quenching at a temperature of about to 65 F'.

While the plate is in the extremely so'ft ccndition the remaining operations in the sequence can be quickly and easily carried out. I have discovered and my invention is based on the discovery that this is particularly true of the McKee treatment step because the softness of the alloy readily permits the production of smoothly graded level differentials in any areas of the plate either large or small as may be required by the nature of the subject. Thisresults in a persists over a period of time ample for carrying out the operations of completing the plate including the McKee treatment so that the rolling aids and accelerates the later toughening of the alloy and helps to put the plate into condition for properly withstanding the wearing and hammering action of long press runs.

It may be remarked that the step of heat treating to the critical temperature with sudden cooling or quenching is advantageous in thecustomary flat plate sequence. In that case such heat treating precedes the shaving of the plate,

and the McKee treatment is combined with the shaving operation by using a built-up matrix on the face of the plate. The equipment used is a standard fiat bed shaving machine having a series of spring pressed rollers operating with the shaving knife. The principle is exactly the same as that of the curved bed shaver used on curved plates. This contrasts with the necessity for applying the McKee treatment in a heated platen hydraulic press as an entirely separateoperation. The extreme softness of the alloy resulting from heating to the critical temperature and suddenly cooling or quenching makes it possible to combine the McKee treating and shaving 0perations. This softness also improves the later curving of the plate resulting in a substantially perfect t for the press cylinder with no tendency to resist the retention of the curved form.-

In heat treating an electrotype printing plate it is exposed to a high temperatureabout 470 F. more or less-for about fifteen minutes, followed by rapid cooling, as by quenching at a temperature of about 45 to 65 F. usually by immersion in a fluid or liquid. In practice the temperature may rise sufficiently to soften the plate, so that if curved it tends to flatten out, and if flat it tends to assume curved or warped form, again the shell ltakes up or absorbs ambient heat more rapidly than the alloy which is a poor conductor of heat so that the shell expands more rapidly than the alloy, causing defects and disadvantages. i

According to my invention the flrst of these difficulties may be avoided by the use of a support for the plate during the heat treatment and the support may be flat or curved; and the second of these difficulties may be avoided by interposing between the face of the support and the shell of the plate heat insulating or non-conducting material, or by otherwise covering the `shell of the plate with such material. In cases where the plate is quenched by immersion the material used for covering purposes should be unaffected by the fiuid in which the plate is immersed. The heat-insulating or non-conducting material serves to minimize the heat absorbed by the shell of the plate and in that way opposes over heating it, and the support opposes deformation of the plate itself.

In the accompanying drawing:

Figure 1 is a perspective view of apparatus useful in applying rolling pressure to the back of a curved partially completed electrotype plate.

Figure 2 is a similar view of apparatus adapted to apply pressure and to trimor shave the back of the plateLand y Figure 3 is an enlarged view illustrating the toothed surface of the roll 3 in Figure 1.

Referring to the drawing, I indicated a. curved machine whose cylinder 2 conforms to the press cylinder. As shown in Figure 1 this machine is provided with rollers 3 having toothed'surfaces and they apply pressure at the back of the curved plate b. As shown in Figure 2 the machine comprises a series of spring pressed rollers 4 which precede a cutting knife -5 and the rollers and knife exert pressure when trimming or shaving at the back of the plate. When such machinery is used in thepractice of the-invention the mat or matrix is applied to the face of the plate b and it is made to produce level differentials corresponding or in consonance with the requirements of the proof of form in respect to gradatlons of light and shade over its entire surface including both large and small areas. This is made possible according to my invention because of the extreme softness of the alloy backing produced by critical heat treatment at a. temperature of about 470 F. followed by rapid cooling or quenching as described.

It will be obvious to those skilled in the art to which the invention relates that modifications may be made in details of procedure and in matters of mere form without departing from the spirit of the invention which is not limited to such matters or v otherwise Athanthe prior art and the appended claims may require. V

I claim: v

1. The improvement in the process of making electrotype printing plates which consists in heating a partially completed electrotype plate to a critical temperature of about 470 F. for about fifteen minutes and then rapidly cooling it as by quenching at a temperature of about 45 to F. thereby developing in the backing up lead alloy softness followed after a time interval by increased hardness and toughness-'in respect to its initial condition, and thereafter and during said time interval and while the -plate is in softened condition imparting toit level dfferentials not only at relatively large but also at relatively small areas of the plate surface by the application of pressure and a mat or matrix corresponding to both small and large surface areas of thev softening their lead alloy and while the lead.

alloy is soft pressing level differentials into the printing face with a mat or matrix corresponding with the subject.

HARRY M. BLAE'IZ. 

